The general method of operation of the type of printhead described in WO 93/11866 is well known, wherein an agglomeration or concentration of particles is achieved in the printhead, and, at the ejection location, the agglomeration of particles is then ejected on to a substrate. In the case of an array printer, plural cells may be arranged in one or more rows.
WO 03/101741 describes a particular arrangement of printhead which comprises an ejector array mounted within a main body, to which an intermediate electrode plate is mounted. Ink is ejected from the ejector array by the action of an electric field generated between electrodes situated within the ejector array and the intermediate electrode as is well understood by the person skilled in the art. Typically, the ejector array is formed as a laminate structure which includes at least an ink inlet manifold, an ink inlet prism, a central tile and an ink outlet manifold. The central tile has the array of ejection points formed along its front edge and both the central tile and the prism include channels for supplying ink to the ejector array. Specifically, in the printhead described in WO 03/101741, a particular shape of ink manifold is chosen which provides desirable ink flow characteristics to and from the ejection locations of the ejection array.
The shape of the inlet manifold of the printhead described in WO 03/101741 comprises a triangular chamber which is divergent in a direction from the inlet of the ink supply (i.e. the position within the manifold at which ink is input from a supply line) to the outlet (the outlet position being a front surface of the manifold along which ink is supplied to the array of ejection locations). The outlet manifold has a similar shape, but which is convergent in a direction from its inlet (which is the surface of the outlet manifold along which surplus ink is returned from the array of ejection locations) to its outlet (i.e. the position within the outlet manifold at which ink is output to a return line).
Whilst providing desirable ink flow characteristics to the array of ejection locations, the shape of the ink manifold described in WO 03/101741 results in inlet/outlet manifolds which have a relatively large width dimension from front to back (i.e. from the ink supply inlet into the inlet manifold to the front surface which connects to the array of the ejection locations or, for the outlet manifold, from the surface which connects to the array of the ejection locations to the ink output position). This necessarily results in a printhead which also has a relatively large width dimension from front to back.
An object of the present invention is to provide a printhead having a significantly reduced width from front to back (i.e. the distance from the array of ejection locations to the rear of the printhead block), but which also retains and improves upon the desirable ink flow characteristics of the printhead described in WO 03/101741.